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Nutrient Digestibility of Growing Pigs Fed Phytase- and Xylanase-Supplemented Wheat-Based Diets with Low, Medium or High Lysine Level
An experiment was conducted to determine the effect of adding xylanase to phytase-supplemented wheat-based diets containing low, medium, or high Lys on apparent ileal digestibility (AID) and apparent total tract digestibility (ATTD) of nutrients in growing pigs. Six ileal-cannulated barrows (initial BW = 39.1±1.6 kg) were fed 6 diets in a 6 × 6 Latin square design. The 6 diets were a phytase-supplemented (500 FTU/kg) wheat-soybean meal-based basal diet with a standardized ileal digestible Lys content of 0.81% (low), 0.91% (medium) or 1.01% (high) and xylanase at 0 or 2,000 XU/kg in a 3 × 2 factorial arrangement. The diets were similar in NE (1.79 Mcal/kg) and CP (25%); and the dietary AA levels were based on ideal AA ratio. The diets only differed in wheat and crystalline AA; the dietary level of AA was increased by increasing the dietary level of crystalline AA at the expense of wheat. All 6 diets contained 0.5% Cr2O3 as an indigestible marker. Dietary Lys level and xylanase interacted (P < 0.05) for AID of energy and all AA except Lys and Trp such that xylanase supplementation increased (P < 0.05) the AID of energy by 11%, and of the AA on average by 9% when the basal diet was low in Lys, but not when the basal diet was medium or high in Lys. Also, dietary Lys level and xylanase tended to interact (P = 0.054) on AID of Lys such that xylanase supplementation increased the AID of Lys only when the basal diet was low in Lys. Xylanase supplementation increased (P < 0.05) AID of Trp from 77.6 to 79.3%, and ATTD of energy from 79.1 to 80.2% regardless of dietary Lys level. In summary, an addition of xylanase to phytase-supplemented wheat-based basal diet for growing pigs can increase the AID and ATTD of energy but also AID of AA for diets limiting in Lys. In conclusion, the results from the present study indicate that diets could be formulated with reduced AA levels to optimize the benefits of xylanase supplementation to increase nutrient and energy digestibility in growing pigs.
Keywords:
lysine, pig, xylanase